Processes for the preparation of methylchlorosilanes by reacting silicon with chloromethane in the direct Muller-Rochow synthesis in the presence of suitable catalysts and catalyst combinations have already been disclosed. For example, U.S. Reissue Pat. No. 33,452 describes a direct synthetic method using a catalyst combination of copper or copper compounds with zinc and tin co-catalysts. The ratio of copper, zinc and tin catalysts to one another has a considerable effect on the process, in particular on productivity and selectivity, while the form in which the catalysts are introduced into the catalyst composition, for example as metal, alloys or compounds, is of secondary importance.
U.S. Pat. No. 4,554,370 describes a process in which silicon is reacted with chloromethane in the presence of copper(I) chloride as catalyst, and in the presence of pyrogenic silicic acid as an anti-agglomerant, to give methylchlorosilanes. The presence of pyrogenic silicic acid is intended to prevent the formation of agglomerates in the "contact mass", composed of silicon and catalysts.